Kissper, a kiwi fruit peptide with channel-like activity: Structural and functional features

Effects of Green and Gold Kiwifruit Varieties on Antioxidant Neuroprotective Potential in Pigs as a Model for Human Adults

Kiwifruit (KF) has shown neuroprotective potential in cell-based and rodent models by augmenting the capacity of endogenous antioxidant systems. This study aimed to determine whether KF consumption modulates the antioxidant capacity of plasma and brain tissue in growing pigs. Eighteen male pigs were divided equally into three groups: (1) bread, (2) bread + Actinidia deliciosa cv. 'Hayward' (green-fleshed), and (3) bread + A. chinensis cv. 'Hort16A' (yellow-fleshed). Following consumption of the diets for eight days, plasma and brain tissue (brain stem, corpus striatum, hippocampus, and prefrontal cortex) were collected and measured for biomarkers of antioxidant capacity, enzyme activity, and protein expression assessments. Green KF significantly increased ferric-reducing antioxidant potential (FRAP) in plasma and all brain regions compared with the bread-only diet. Gold KF increased plasma ascorbate concentration and trended towards reducing acetylcholinesterase activity in the brain compared with the bread-only diet. Pearson correlation analysis revealed a significant positive correlation between FRAP in the brain stem, prefrontal cortex, and hippocampus with the total polyphenol concentration of dietary interventions. These findings provide exploratory evidence for the benefits of KF constituents in augmenting the brain's antioxidant capacity that may support neurological homeostasis during oxidative stress.

Plant and Arthropod IgE-Binding Papain-like Cysteine Proteases: Multiple Contributions to Allergenicity

Papain-like cysteine proteases are widespread and can be detected in all domains of life. They share structural and enzymatic properties with the group's namesake member, papain. They show a broad range of protein substrates and are involved in several biological processes. These proteases are widely exploited for food, pharmaceutical, chemical and cosmetic biotechnological applications. However, some of them are known to cause allergic reactions. In this context, the objective of this review is to report an overview of some general properties of papain-like cysteine proteases and to highlight their contributions to allergy reactions observed in humans. For instance, the literature shows that their proteolytic activity can cause an increase in tissue permeability, which favours the crossing of allergens through the skin, intestinal and respiratory barriers. The observation that allergy to PLCPs is mostly detected for inhaled proteins is in line with the reports describing mite homologs, such as Der p 1 and Der f 1, as major allergens showing a frequent correlation between sensitisation and clinical allergic reactions. In contrast, the plant food homologs are often digested in the gastrointestinal tract. Therefore, they only rarely can cause allergic reactions in humans. Accordingly, they are reported mainly as a cause of occupational diseases.

The Effect of Calcium Ions on hIAPP Channel Activity: Possible Implications in T2DM

The calcium ion (Ca2+) has been linked to type 2 diabetes mellitus (T2DM), although the role of Ca2+ in this disorder is the subject of intense investigation. Serum Ca2+ dyshomeostasis is associated with the development of insulin resistance, reduced insulin sensitivity, and impaired glucose tolerance. However, the molecular mechanisms involving Ca2+ ions in pancreatic β-cell loss and subsequently in T2DM remain poorly understood. Implicated in the decline in β-cell functions are aggregates of human islet amyloid polypeptide (hIAPP), a small peptide secreted by β-cells that shows a strong tendency to self-aggregate into β-sheet-rich aggregates that evolve toward the formation of amyloid deposits and mature fibrils. The soluble oligomers of hIAPP can permeabilize the cell membrane by interacting with bilayer lipids. Our study aimed to evaluate the effect of Ca2+ on the ability of the peptide to incorporate and form ion channels in zwitterionic planar lipid membranes (PLMs) composed of palmitoyl-oleoyl-phosphatidylcholine (POPC) and on the aggregation process of hIAPP molecules in solution. Our results may help to clarify the link between Ca2+ ions, hIAPP peptide, and consequently the pathophysiology of T2DM.

Evolutionary reconstruction, nomenclature and functional meta-analysis of the Kiwellin protein family

Crop diseases caused by pathogens critically affect global food security and plant ecology. Pathogens are well adapted to their host plants and have developed sophisticated mechanisms allowing successful colonization. Plants in turn have taken measures to counteract pathogen attacks resulting in an evolutionary arms race. Recent studies provided mechanistic insights into how two plant Kiwellin proteins from Zea mays mitigate the activity of the chorismate mutase Cmu1, a virulence factor secreted by the fungal pathogen Ustilago maydis during maize infection. Formerly identified as human allergens in kiwifruit, the biological function of Kiwellins is apparently linked to plant defense. We combined the analysis of proteome data with structural predictions to obtain a holistic overview of the Kiwellin protein family, that is subdivided into proteins with and without a N-terminal kissper domain. We found that Kiwellins are evolutionarily conserved in various plant species. At median five Kiwellin paralogs are encoded in each plant genome. Structural predictions revealed that Barwin-like proteins and Kiwellins cannot be discriminated purely at the sequence level. Our data shows that Kiwellins emerged in land plants (embryophyta) and are not present in fungi as suggested earlier. They evolved via three major duplication events that lead to clearly distinguishable subfamilies. We introduce a systematic Kiwellin nomenclature based on a detailed evolutionary reconstruction of this protein family. A meta-analysis of publicly available transcriptome data demonstrated that Kiwellins can be differentially regulated upon the interaction of plants with pathogens but also with symbionts. Furthermore, significant differences in Kiwellin expression levels dependent on tissues and cultivars were observed. In summary, our study sheds light on the evolution and regulation of a large protein family and provides a framework for a more detailed understanding of the molecular functions of Kiwellins.

Chronic Constipation: Is a Nutritional Approach Reasonable?

Chronic constipation (CC) is one of the most common gastroenterological diagnoses in clinical practice. Treatment includes several steps, depending on the severity of symptoms. Lifestyle modifications and increased intake of fiber and water are suggested by most health professionals. Unfortunately, the recommendations in this regard are the most varied, often conflicting with each other and not always based on solid scientific arguments. This paper aims to clarify this topic by providing practical indications for the management of these patients in every day clinical practice. The literature available on this topic is scarce, and dietary studies have important methodological biases. However, fiber, mainly by binding water and acting as bulking agents and/or as prebiotics for the intestinal microbiota, and mineral water, especially if rich in magnesium and/or bicarbonate, are useful tools. An adequate, well-designed diet should be a cornerstone of any effective treatment for chronic constipation. High-quality studies on larger samples are mandatory to give scientific validity to the role of the food in CC therapy and to enable professionals to choose the best approach for their patients, combining nutritional and pharmacological agents.

Isolation and functionalities of bioactive peptides from fruits and vegetables: A reviews

Bioactive peptides have recently gained more research attention as potential therapies for the management of bodily disorders and metabolic syndromes of delicate health importance. On another note, there is a rising trend on a global scale for the consumption and adoption of fruit and vegetables for the fulfilment of dietary and health needs. Furthermore, fruits and vegetables are being more studied as base materials for the isolation of biologically functional components and accordingly, they have been investigated for their concomitant bioactive peptides. This review focuses on isolation and bio-functional properties of bioactive peptides from fruits and vegetables. This manuscript is potential in serving as a material collection for fundamental consultancy on peptides derived from fruits and vegetables, and further canvasses the necessitation for the use of these food materials as primal matter for such.

Green kiwifruit extracts protect motor neurons from death in a spinal muscular atrophy model in Caenorhabditis elegans

Kiwifruit is considered a functional food and a good source of nutraceuticals. Among the possible beneficial effects of kiwifruit species, a neuroprotective activity exerted in rats with learning and memory impairment induced by exposure to different chemicals was reported. We sought to investigate the neuroprotective activities of kiwifruit toward spinal muscular atrophy (SMA). To this purpose, we have used a recently developed Caenorhabditis elegans SMA model, displaying an age-dependent degeneration of motor neurons detected as locomotory defects, disappearance of fluorescent markers, and apoptotic death of targeted neurons. Although an anti-nematode activity is reported for kiwifruit, it has been verified that neither green (Actinidia deliciosa, cultivar Hayward) nor gold (Actinidia chinensis, cultivar Hort 16A) kiwifruit extracts cause detectable effects on wild-type C. elegans growth and life cycle. Conversely, green kiwifruit extracts have a clear effect on the C. elegans SMA model by partially rescuing the degeneration and death of motor neurons and the locomotion impairment. The gold species does not show the same effect. The components responsible for the neuroprotection are macromolecules with a molecular weight higher than 3 kDa, present in the green and not in the yellow kiwifruit. In conclusion, this is the first study reporting a protective activity of green kiwifruit toward motor neurons. In addition, we demonstrate that C. elegans is an animal model suitable to study the biological activities contained in kiwifruit. Therefore, this model can be exploited for future investigations aimed at identifying kiwifruit molecules with potential applications in the field of human health.

A Peptide from Kiwifruit Exerts Anti-Inflammatory Effects in Celiac Disease Mucosa

Objective: Celiac disease is an immune-mediated disease of the intestine triggered by gluten. Gluten elicits, in genetically susceptible individuals, cytokine responses that are then transmitted to the immunocompetent cells. Vegetables and fruit have anti-inflammatory and antioxidant properties with a protective effect on intestinal epithelium. Kiwifruit is known to have beneficial effects on the intestinal tissues, and it is the only plant food containing the peptide kissper, with anti-inflammatory properties. The aim of this study was the evaluation of the kissper effect on the gluten-induced inflammation in celiac disease. Methods: We used an in vitro model of intestinal culture explant from celiac disease patients and non-celiac disease patients, cultured for 24 hours with the toxic gliadin peptide P31-43 and kissper preincubation. Results: Our data showed HLA-DR and TG2 reduction in the celiac disease mucosa pretreated with kissper, as well as a reduction of COX-2 in two patients. No differences we observed for the TGF-b1 and IL-15 levels in supernatants upon kissper pretreatment. Conclusions: The preliminary results suggest that kissper has a potential anti-inflammatory role in celiac disease.

The nutritional and health attributes of kiwifruit: a review

PURPOSE

To describe the nutritional and health attributes of kiwifruit and the benefits relating to improved nutritional status, digestive, immune and metabolic health. The review includes a brief history of green and gold varieties of kiwifruit from an ornamental curiosity from China in the 19th century to a crop of international economic importance in the 21st century; comparative data on their nutritional composition, particularly the high and distinctive amount of vitamin C; and an update on the latest available scientific evidence from well-designed and executed human studies on the multiple beneficial physiological effects. Of particular interest are the digestive benefits for healthy individuals as well as for those with constipation and other gastrointestinal disorders, including symptoms of irritable bowel syndrome. The mechanisms of action behind the gastrointestinal effects, such as changes in faecal (stool) consistency, decrease in transit time and reduction of abdominal discomfort, relate to the water retention capacity of kiwifruit fibre, favourable changes in the human colonic microbial community and primary metabolites, as well as the naturally present proteolytic enzyme actinidin, which aids protein digestion both in the stomach and the small intestine. The effects of kiwifruit on metabolic markers of cardiovascular disease and diabetes are also investigated, including studies on glucose and insulin balance, bodyweight maintenance and energy homeostasis.

CONCLUSIONS

The increased research data and growing consumer awareness of the health benefits of kiwifruit provide logical motivation for their regular consumption as part of a balanced diet. Kiwifruit should be considered as part of a natural and effective dietary strategy to tackle some of the major health and wellness concerns around the world.

Putative mechanisms of kiwifruit on maintenance of normal gastrointestinal function

Kiwifruits are recognized as providing relief from constipation and symptoms of constipation-predominant irritable bowel syndrome (IBS-C). However, the underlying mechanisms, specifically in regards to gastrointestinal transit time and motility, are still not completely understood. This review provides an overview on the physiological and pathophysiological processes underlying constipation and IBS-C, the composition of kiwifruit, and recent advances in the research of kiwifruit and abdominal comfort. In addition, gaps in the research are highlighted and scientific studies of other foods with known effects on the gastrointestinal tract are consulted to find likely mechanisms of action. While the effects of kiwifruit fiber are well documented, observed increases in gastrointestinal motility caused by kiwifruit are not fully characterized. There are a number of identified mechanisms that may be activated by kiwifruit compounds, such as the induction of motility via protease-activated signaling, modulation of microflora, changes in colonic methane status, bile flux, or mediation of inflammatory processes.

Influence of Geographical Location of Orchards on Green Kiwifruit Bioactive Components

Italy is one of the world's major kiwifruit producers and exporters with orchards located in different areas from the north to the south of the peninsula. This study sought to investigate for the first time the possible influence of the geographical location of kiwifruit orchards on some fruit components, selected because of their involvement in beneficial or negative effects on human health. The fruits harvested in 16 Italian areas were analyzed, and the results obtained show that the observed variations of the relative amounts of total proteins, kiwellin, the major allergen actinidin, ascorbate, polyphenols, and superoxide dismutase (SOD)-like activity seem not to be related to the geographical location of the orchards. In contrast, the high concentration of the nutraceutical peptide kissper seems to have some relationship with the cultivation area. In fact, its amount is much higher in the fruits from the Lazio region, thus providing added value to these kiwifruits.

Elusive Structural, Functional, and Immunological Features of Act d 5, the Green Kiwifruit Kiwellin

Kiwellin (Act d 5) is an allergenic protein contained in kiwifruit pulp in high amounts. The aim of this study was to investigate the three-dimensional structure of the natural molecule from green kiwifruit and its possible function. Kiwellin was crystallized, and its structure, including post-translational modifications, was elucidated. The molecular weight and structural features, in solution, were analyzed by gel filtration and circular dichroism, respectively. Although structurally similar to expansin, kiwellin lacks expansin activity and carbohydrate binding. A specific algorithm was applied to investigate any possible IgE reactivity correlation between kiwellin and a panel of 102 allergens, including expansins and other carbohydrate-binding allergens. The available data suggest a strong dependence of the kiwellin structure on the environmental/experimental conditions. This dependence therefore poses challenges in detecting the correlations between structural, functional, and immunological features of this protein.

Crystal structure of kiwellin, a major cell-wall protein from kiwifruit

Kiwellin is a cysteine-rich, cell wall-associated protein with no known structural homologues. It is one of the most abundant proteins in kiwifruit (Actinidia spp.), and has been shown to be recognised by IgE of some patients allergic to kiwifruit. Cleavage of kiwellin into an N-terminal 4 kDa peptide called kissper and a core domain called KiTH is mediated by actinidin in vitro, and isolation of the kissper peptide from green-fleshed kiwifruit extracts suggested it may result from in vivo processing of kiwellin. In solution, kissper is highly flexible and displays pore-forming activity in synthetic lipid-bilayers. We present here the 2.05 Å resolution crystal structure of full-length kiwellin, purified from its native source, Actinidia chinensis (gold-fleshed kiwifruit). The structure confirms the modularity of the protein and the intrinsic flexibility of kissper and reveals that KiTH harbours a double-psi β-barrel fold hooked to an N-terminal β hairpin. Comparisons with structurally-related proteins suggest that a deep gorge located at the protein surface forms a binding site for endogenous ligands.

The kiwi fruit peptide kissper displays anti-inflammatory and anti-oxidant effects in in-vitro and ex-vivo human intestinal models

Literature reports describe kiwi fruit as a food with significant effects on human health, including anti-oxidant and anti-inflammatory activity. Fresh fruit or raw kiwi fruit extracts have been used so far to investigate these effects, but the molecule(s) responsible for these health-promoting activities have not yet been identified. Kissper is a kiwi fruit peptide displaying pore-forming activity in synthetic lipid bilayers, the composition of which is similar to that found in intestinal cells. The objective of this study was to investigate the kissper influence on intestinal inflammation using cultured cells and ex-vivo tissues from healthy subjects and Crohn's disease (CD) patients. The anti-oxidant and anti-inflammatory properties of kissper were tested on Caco-2 cells and on the colonic mucosa from 23 patients with CD, by challenging with the lipopolysaccharide from Escherichia coli (EC-LPS) and monitoring the appropriate markers by Western blot and immunofluorescence. EC-LPS challenge determined an increase in the intracellular concentration of calcium and reactive oxygen species (ROS). The peptide kissper was highly effective in preventing the increase of LPS-induced ROS levels in both the Caco-2 cells and CD colonic mucosa. Moreover, it controls the calcium increase, p65-nuclear factor (NF)-kB induction and transglutaminase 2 (TG2) activation inflammatory response in Caco-2 cells and CD colonic mucosa. Kissper efficiently counteracts the oxidative stress and inflammatory response in valuable model systems consisting of intestinal cells and CD colonic mucosa. This study reports the first evidence supporting a possible correlation between some beneficial effects of kiwi fruit and a specific protein molecule rather than generic nutrients.

Comparative transcript profiling by SuperSAGE identifies novel candidate genes for controlling potato quantitative resistance to late blight not compromised by late maturity

Resistance to pathogens is essential for survival of wild and cultivated plants. Pathogen susceptibility causes major losses of crop yield and quality. Durable field resistance combined with high yield and other superior agronomic characters are therefore, important objectives in every crop breeding program. Precision and efficacy of resistance breeding can be enhanced by molecular diagnostic tools, which result from knowledge of the molecular basis of resistance and susceptibility. Breeding uses resistance conferred by single R genes and polygenic quantitative resistance. The latter is partial but considered more durable. Molecular mechanisms of plant pathogen interactions are elucidated mainly in experimental systems involving single R genes, whereas most genes important for quantitative resistance in crops like potato are unknown. Quantitative resistance of potato to Phytophthora infestans causing late blight is often compromised by late plant maturity, a negative agronomic character. Our objective was to identify candidate genes for quantitative resistance to late blight not compromised by late plant maturity. We used diagnostic DNA-markers to select plants with different field levels of maturity corrected resistance (MCR) to late blight and compared their leaf transcriptomes before and after infection with P. infestans using SuperSAGE (serial analysis of gene expression) technology and next generation sequencing. We identified 2034 transcripts up or down regulated upon infection, including a homolog of the kiwi fruit allergen kiwellin. 806 transcripts showed differential expression between groups of genotypes with contrasting MCR levels. The observed expression patterns suggest that MCR is in part controlled by differential transcript levels in uninfected plants. Functional annotation suggests that, besides biotic and abiotic stress responses, general cellular processes such as photosynthesis, protein biosynthesis, and degradation play a role in MCR.

The kiwi fruit peptide kissper displays anti-inflammatory and anti-oxidant effects in in-vitro and ex-vivo human intestinal models

Literature reports describe kiwi fruit as a food with significant effects on human health, including anti-oxidant and anti-inflammatory activity. Fresh fruit or raw kiwi fruit extracts have been used so far to investigate these effects, but the molecule(s) responsible for these health-promoting activities have not yet been identified. Kissper is a kiwi fruit peptide displaying pore-forming activity in synthetic lipid bilayers, the composition of which is similar to that found in intestinal cells. The objective of this study was to investigate the kissper influence on intestinal inflammation using cultured cells and ex-vivo tissues from healthy subjects and Crohn's disease (CD) patients. The anti-oxidant and anti-inflammatory properties of kissper were tested on Caco-2 cells and on the colonic mucosa from 23 patients with CD, by challenging with the lipopolysaccharide from Escherichia coli (EC-LPS) and monitoring the appropriate markers by Western blot and immunofluorescence. EC-LPS challenge determined an increase in the intracellular concentration of calcium and reactive oxygen species (ROS). The peptide kissper was highly effective in preventing the increase of LPS-induced ROS levels in both the Caco-2 cells and CD colonic mucosa. Moreover, it controls the calcium increase, p65-nuclear factor (NF)-kB induction and transglutaminase 2 (TG2) activation inflammatory response in Caco-2 cells and CD colonic mucosa. Kissper efficiently counteracts the oxidative stress and inflammatory response in valuable model systems consisting of intestinal cells and CD colonic mucosa. This study reports the first evidence supporting a possible correlation between some beneficial effects of kiwi fruit and a specific protein molecule rather than generic nutrients.

Diversity and relative levels of actinidin, kiwellin, and thaumatin-like allergens in 15 varieties of kiwifruit (Actinidia)

In the last 30 years the incidence of kiwifruit allergy has increased with the three major allergenic proteins being identified as actinidin, kiwellin, and thaumatin-like protein (TLP). We report wide variation in the levels of actinidin and TLP in 15 kiwifruit varieties from the four most widely cultivated Actinidia species. Acidic and basic isoforms of actinidin were identified in Actinidia deliciosa 'Hayward' and Actinidia arguta 'Hortgem Tahi', while only a basic isoform of actinidin was identified in Actinidia chinensis 'Hort16A'. One isoform each of kiwellin and TLP were identified in ripe fruit. The cysteine protease activity of actinidin correlated with protein levels in all species except A. arguta. Protein modeling suggested that modifications to the S2 binding pocket influenced substrate specificity of the A. arguta enzyme. Our results indicate that care is necessary when extrapolating allergenicity results from single varieties to others within the same and between different Actinidia species.

Kiwifruit modulation of gastrointestinal motility

Disorders of gastrointestinal motility are common, resulting in a decreased quality of life of individuals, and an economic burden. Gastrointestinal motility is categorized according to location within the gastrointestinal tract: stomach, small intestine, and colon, with the colon being the dominant compartment in determining overall gastrointestinal transit. Constipation results from gastrointestinal dysmotility and is a significant chronic health issue globally. Clinical studies in a range of adult populations consistently indicate that kiwifruit are a highly effective dietary option to promote laxation. This, together with emerging evidence for the putative effects of kiwifruit in beneficially promoting gastric emptying and digesta mixing, suggests that kiwifruit are physiologically active throughout the gastrointestinal tract. Although the mechanisms of this action remain unknown, the unique behavior of kiwifruit fiber during digestion and the potential action of bioactive components in kiwifruit may contribute to the effectiveness of kiwifruit in modulating gastrointestinal motility.

Kiwifruit proteins and enzymes: actinidin and other significant proteins

Protein is a minor but significant component of kiwifruit. Crude protein is typically measured at about 1% of fresh weight; however, soluble protein is much less, around 0.3%. The difference can be accounted for by nonprotein nitrogen and insoluble protein, such as polypeptide chains forming part of the cell wall. Kiwifruit soluble protein is mostly accounted for by the proteolytic enzyme actinidin and its inactive forms, a so-called thaumatin-like protein and an unusual protein called kiwellin, which has no known function. Actinidin is the predominant enzyme in kiwifruit and can play a role in aiding the digestive process. There is also a wide range of enzymes involved in the ripening of kiwifruit, particularly enzymes involved in polysaccharide and oligosaccharide metabolism and in the development of flavor and aroma compounds. Whether the enzymatic actions of these have any effect during the consumption and digestion of kiwifruit is not known, although any noticeable effect is unlikely. Some enzymes are likely to have an effect on flavor, texture, and nutritional values, during storage, processing, and preparation of kiwifruit.

Heard it through the grapevine: proteomic perspective on grape and wine

Grapevine (Vitis ssp.) is currently considered as the most important fruit plant throughout the world, both due to its economic importance and to its role as a non climacteric model species. The relevance of the studies devoted to the dissection of grapevine biology and biochemistry underlines the great amount of attention that this plant has attracted over the last decade. The milestones among these studies are represented by the accomplishment of the genome sequencing programmes in 2007 [1,2]. Since then, the investigation of grape OMICS has been implemented, and the number of reports published on grape and wine protein investigations using proteomic techniques have significantly improved knowledge in the field.